"Passive" restraint apparatus which requires no action by a vehicle occupant to make operative, as contrasted to "active" restraint apparatus requiring a conscious effort by an occupant to become operative (such as conventional seat belts) are more commonly being installed in motor vehicles as the result of government agency, insurance industry and consumer pressures. Experience and testing have shown that the most effective passive occupant restraint approach is to abruptly (in a matter of milliseconds) inflate a safety bag automatically in response to a sudden change in vehicle velocity occasioned by a high impact accident. The inflated safety bag pins the occupant in his/her seat, well cushioned from the effects of the accident for an interval sufficient to prevent serious injury.
The mechanics for timely safety bag inflation are basically of two types. One type involves storing a liquidfied gas under high pressure in a reservoir. On impact, the liquidfied gas is allowed to escape and convert to its gaseous form, inflating the safety bag. The approach has numerous disadvantages. The bulk and weight of the components for handling the gas-producing liquid makes it difficult and expensive to package the safety apparatus in the steering columns and dashboards of the motor vehicles Storage integrity over a long time period of widely varying ambient conditions is tenuous at best. Moreover, the most effective and practical gas-producing liquids are chlorofluorocarbons, such as FREON, which have adverse effects on the environment.
As a consequence, safety bag inflation through the release of liquidfied gas has largely been supplanted by the use of ignitable propellants capable of rapidly generating large volumes of gas by exothermic reaction. Heretofore, the propellants have invariably been in a solid or granular form comprised of low energy compositions, such as an alkalai metal azide, cupric oxide, boron nitrate, etc. The solid propellants need not be stored under pressure, are stable over time and varying ambient conditions, and are convenient to package in a passive restraint apparatus. There is however a significant drawback to the use of solid propellants of this type, in that the generated gas contains toxic by-products and particulate matter. As a consequence, the safety bag inflating gases must first be filtered to remove the toxic by-products and also to catch combusting particulate matter which is capable of burning holes in the safety bag. These filters increase the size, weight and cost of a passive restraint apparatus.
It is accordingly an object of the present invention to provide an improved apparatus for exothermically generating large volumes of gas to deploy an inflatable member.
A further object is to provide apparatus of the above-character for abruptly inflating an occupant restraint safety bag in a motor vehicle.
An additional object is to provide occupant restraint apparatus of the above-character, wherein the generated gas is inherently free of potentially harmful byproducts.
Another object is to provide occupant restraint apparatus of the above-character, which is simple in construction, light weight, compact, and reliable in operation.
Other objects of the invention will in part be obvious and in part appear hereinafter.